I'm not totally sure, but it sounds like you are using the 6.50's. Pretty decent drivers, though a tad old. I did notice an occasional 'jitter' in D3D games, but it was minute at worst. I've used the NVidia 12.41s, and am currently using Guillemot's 14.10's. Haven't tried XP yet, but I can recommend any of the two above (provided you're using a Guillemot card with the Guillemot drivers

).